Cosmological Collider Signatures of Higgs-$R^2$ Inflation

Understand

We study the cosmological collider signatures in the Higgs-$R^2$ inflation model.

• We consider two distinct types of signals: one originating from the inflaton coupling to Standard Model fermions and gauge bosons, and another arising from the isocurvature mode interaction with the inflaton.
• In the former case, we determine that the signal magnitude is likely too small for detection by upcoming probes, primarily due to suppression by both the Planck scale and slow-roll parameters.
• However, we provide a detailed computation of the signal which could be potentially applicable to various Higgs inflation variants.